Method of inhibiting the corrosive effect of sulfuric acid



Patented June 27, 195

METHOD OF ITING THE CORROSIVE EFFECT OF SULFURIC ACID Martin S. Baer, Baytown, Tex., assignor to Standard Oil Development Company, a corporation of Delaware N Drawing. Application November 27, 1944, Serial No. 565,401

3 Claims. (01. 23-167) The present invention is directed to an inhibited aqueous sulfuric acid and a method for inhibiting corrosion by such acid.

The present invention is based on the discovery that the corrosiveness of aqueous sulfuric acid for ferrous metals can be substantially reduced by incorporating in the acid an effective amount of boron trifluoride. -To illustrate the effect of boron trifluoride on the corrosiveness of aqueous sulfuric acid, the following data were obtained by immersion of steel strips in the specifled acids at room temperature:

Constituent:

Hrs

0a.-.. 100 76 03:804."... 100 76.2 87.3 98 I- 24 23. 8 l2. 7 2 Corrosiveness:

Peuetratlonin/yr. 0.04 0.0113 0.11 0.0006 0.0069 0.0614

This table shows that the corrosiveness to steel of 80% sulfuric acid was reduced by about 71% by the addition of 24% by weight of boron trifluoride to the acid. In like manner, the corrosiveness of 60% acid was reduced by about 94 92 by the addition thereto of 23.8% of boron trifluoride, by about 93% by the addition of 12.?

weight percent of boron trlfluoride. and by about 43% by the addition of 2 weight percent of boron trifluoride. Thus, it will be seen that the boron trifluoride is eifective for corrosion inhibiting purposes in aqueous sulfuric acid in amounts varying from about 2% to about 30%. The boron trifiuoride has the additional virtue that it will not ordinarily interfere with the purposes for which the sulfuric acid is employed. especially in refinery operations.

The nature and objects of the present invention having been thus described and illustrated. what is claimed as new and useful and is desired to be secured by Letters Patent is:

l. A method for inhibiting the corrosivity of a solution consisting of aqueous sulfuric acid having a strength no greater than 80% by weight H2804 in contact with a ferrous metal surface normally corrodible by said acid which consists in adding to said acid an amount of boron trifiuoride in the range between 2% and by weight.

2. A method for inhibiting the corrosivity of a solution consisting of aqueous sulfuric acid having a strength in the range between and to H2804 in contact with a ferrous metal surface normally corrodible by said acid which consists in adding to said acid an amount of boron mfluoride in the range between 2% and 30% by weight.

3. A method for inhibiting the corrosivity of a solution consisting of aqueous sulfuric acid having a strength in the range between 60% and 80% by weight H2504 in contact with a ferrous metal surface normally corrodible by said acid which consists in addin: to said acid an amount of boron trifiuoride in the range between 2% and 24% by weight.

S. BAER.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 2.133.452 Hewlett Oct. 18. 1938 2,257.02? Vesterdel Sept. 30, 194i C' 'THER REFERENCES Mellor, Comp. Treatise in Inorganic and Them retical Chemistry, vol. 5. 1928 ed.. page 122. 

1. A METHOD OF INHIBITING THE CORROSIVITY OF A SOLUTION CONSISTING OF AQUEOUS SULFURIC ACID HAVING A STRENGTH NO GREATER THAN 80% BY WEIGHT H2SO4 IN CONTACT WITH A FERROUS METAL SURFACE NORMALLY CORRODIBLE BY SAID ACID WHICH CONSISTS IN ADDING TO SAID ACID AN AMOUNT OF BORON TRIFLURIDE IN THE RANGE BETWEEN 2% AND 30% BY WEIGHT. 